The present invention relates generally to a fuel enrichment apparatus for a fuel mixer or carburetor. More specifically the invention is directed to a gaseous type carburetor utilizing a gaseous fuel combustible in an internal combustion engine. The added distinction of this invention is that it can be applied to either an air valve carburetor or to a carburetor with a fixed venturi. The invention is, therefore, applicable to a dual fuel type carburetor, that is, a carburetor or carburetor tandem that will operate with either liquid or gaseous fuel although the enrichment arrangement functions only during the gaseous operation.
The enrichment aspect of the invention is engageable at the start-up or cranking of an internal combustion engine to aid in starting, and is also available to induce supplemental fuel at wide open throttle or heavy load.
Prior art carburetors had various devices for idle control and for supplemental fuel at wide open throttle. Many supplemental fuel devices are known for liquid fuel carburetors in conjunction with a fixed venturi in the induction passage. Still other devices have shown idle assist devices for liquid petroleum (LP), gas fuel mixers and have included devices utilizing high pressure lines from the primary side of an LP gas evaporator rather than utilizing the low pressure fuel of the secondary side of the LP gas evaporator.
The present structure can be utilized in a fixed venturi type carburetor, but it can also be applied to an air valve type carburetor wherein it is generally considered that this type carburetor has a variable venturi such that the flow rate may be variable but the pressure head is constant in the induction passage above the throttle plate. The invention monitors the low pressure gas of the main fuel supply line. At start-up of an internal combustion engine there is little or no manifold vacuum and, therefore, insufficient low pressure in the induction passage to open the air valve in an air valve carburetor and induct fuel through the induction passage. There is, however a slight pressure depression below atmospheric pressure just above the throttle plate. This pressure depression is about six (6) inches of water column (6" w.c.). At the cranking of an engine additional fuel near the throttle plate is required for starting, and at full throttle added fuel is required to satisfy the added load. At idle or at cruising speed the pressure drop in the induction passage is adequate to actuate opening of an air valve and is sufficient to induce gas past a fuel metering cone into the engine for combustion; therefore, fuel enrichment is not required at idle or cruising speeds. Should the engine revolutions per minute (RPM) decline at wide open throttle due to an overload condition, there would be a change in the manifold vacuum below that necessary to open the air valve to allow adequate fuel for the engine. The fuel enrichment apparatus would respond to such a condition so as to supplement the main fuel supply under the changed vacuum condition.